The present invention relates to theft prevention and more particularly to electronic theft prevention that uses existing wiring in an automobile.
Presently, many individuals have alarm systems installed in their automobiles in order to deter theft and vandalism. Alarm systems evolve in complexity as the abilities of thieves and vandals improve.
The present state of the art in automobile alarms is to include a digital control unit attached to peripheral equipment which implements various anti-theft features. This equipment usually includes an ignition disable and a siren. For most alarm systems, it is desirable to hide the location of these devices to prevent the thief from discerning their location and defeating their operation.
Unfortunately, installation of these devices requires that installers run new wiring to interconnect the components (e.g., U.S. Pat. Nos. 4,792,792, 4,992,670 and 5,061,915). This extra wiring is a tell-tale sign allowing the devices' hiding places to be discovered. In addition, the wiring as an add-on may be unsightly, and in some instances, the attaching of additional wiring is difficult or impossible. Finally, the extra wiring provides another weak link in the alarm system because many alarm functions are disabled by cutting particular wires of the system (e.g., the newly added wires which provide a medium for the transmission and reception of signals between the various components of the alarm system). Often, a controller for an alarm system is a relatively large box, having many wires connecting the controller to various sensors and actuators. For conventional systems, signals are sent on analog format or in "on/off" format. To preserve integrity of such a prior art system, the controller must be well-hidden, as well as the wires heading up to it, because disconnection of the additional wires will disable the theft system.
Examples illustrating difficult wiring situations in automotive vehicles include (1) adding wiring between the engine compartment and the passenger compartment and (2) adding power door locks or window functions to the alarm system. When wiring from the engine compartment enters the passenger compartment, it must pass through a grommet such that the majority of the environment and noise from the engine compartment is deterred from entering the passenger compartment. This grommet has scant spare room for the addition of wiring for an alarm system. To install wiring for the control of power locks and windows, the vehicles doors must be dismantled and then reassembled.